This invention relates to regenerative braking and driving apparatus for vehicles and more particularly to a braking and driving apparatus which serves to brake a vehicle while simultaneously storing kinetic energy and which harnesses such energy to drive the vehicle forward when the brake is released.
It is known to store kinetic energy from a bicycle when it is coasting or travelling down an incline and to use that energy later when the bicycle is travelling uphill. There are many patents which describe mechanisms for storing such energy in a coil or spiral spring and for harnessing that energy to propel a bicycle forward. In some patents, the energy is generated at the chainwheel or the sprocket to which the pedals are attached. Examples of such patents are U.S. Pat. No. 4,305,599 to Houston; U.S. Pat. No. 6,053,830 to Glaeser; U.S. Pat. No. 2,908,356 to Daarud; and U.S. Pat. No. 2,638,359 to Crumble.
Known mechanisms, such as those enumerated above, have a number of disadvantages. For example, while the spring is being charged, the energy that would otherwise be used to propel the vehicle is used to charge the spring. In some cases the rider has no option about when charging occurs. Charging may, for example, occur at a time when the rider would prefer that all the energy he is expending be used to propel the bicycle forward such as when he is travelling up an incline or he is accelerating.
In other cases, a lever is provided for selecting when energy is to be stored in the coil spring. In those cases, the rider must consciously manipulate the lever. If the rider is travelling in a hilly or alpine terrain when he has to make many turns and to apply the brakes constantly in a short space of time, he may not have sufficient time to use the lever to make effective use of the energy storage capabilities of the mechanism.
In U.S. Pat. No. 6,035,970 to Conte the energy is captured at the wheel of the bicycle. In that patent, a roller at the rim of a wheel charges a coil spring which is mounted to a cross bar of the bicycle. The roller is only engaged when the brake is applied. A lever on the handlebar allows the rider to use the energy to propel the vehicle when he chooses to do so.
The apparatus described in Conte does not share many of the disadvantages of the other patents enumerated above but it has other disadvantages. First, the roller may not work very well when the bicycle is being ridden in rain and the rim of the wheel is slick. Secondly, the roller may become jammed by a stick, pebble or other obstruction. Thirdly, the roller activates a cable which is mounted at a distance from the roller and energy is lost between the roller and the coil. Fourthly the device is activated by a lever at the handlebar and is inconvenient to use in hilly or alpine terrain for the reasons mentioned above.
The braking and driving apparatus of the subject invention has none of the disadvantages of the known apparatuses described above. The apparatus includes a torsional spring which rotates with the wheel until the rate of rotation of one end is decreased relative to the other end. Rotation of the end can be decreased by various means such as by a brake, a clutch, a ratchet, balls and detents and a friction plate. Each of these means causes the spring to deform and in that sense is a xe2x80x9cdeforming meansxe2x80x9d. As the rate of rotation of the end decreases, the spring deforms elastically and the rate of the other end likewise decreases.
In the detailed description of the invention, the deforming means is a brake but it is to be understood that other mechanisms are also suitable As long as the mechanism is capable of stopping one end of the coil spring from rotating relative to the other it is suitable.
If a brake is used to decrease the rate of rotation of one end of the spring, that end is preferably affixed to a concentric brake drum mounted about an axle of the vehicle. When the brake is applied, the drum ceases to rotate with the wheel of the vehicle and remains stationary relative to the vehicle. At this time the spring deforms elastically and causes the other end of the spring to activate a ratchet apparatus. That apparatus ensures that the wheel does not rotate faster than the end. The spring thus causes the wheel to decelerate. In other words, the spring acts as a brake for the wheel.
When the braking force is relieved, rotation of the drum will be opposed by one ratchet between a slip sleeve and the brake drum. Torque from the spring will cause the slip sleeve to advance by rotating through a small angle. Such rotation will cause a second ratchet to disengage by depression of its engaged pawls. The tendency of the spring to unwind will be opposed by a third ratchet between a stationary shaft and a retainer for the spring. As the spring unwinds, the vehicle is driven forward until the kinetic energy stored in the spring is dissipated at which time the slip sleeve will return by rotating backward through the small angle and permit the second ratchet to re-engage.
While the braking and driving apparatus of the invention has application in many different vehicles such as bicycles, golf carts, solar vehicles, mopeds and go-carts, the apparatus that will be described in detail below is one used to brake a bicycle. The means for causing the rate of rotation of one end of the coil spring to decrease relative to the other is a conventional brake having a pad and a drum but, as indicated above, other means may be used to produce the same result.
Currently, a typical bicycle is braked manually by means of frictional forces acting on a brake pad and rim, drum or disc interface. The kinetic energy of the rider of the bicycle and the bicycle at a given velocity is dissipated almost entirely by this frictional force. The energy is lost primarily to heat, wear on the braking surfaces and vibration.
For an application such as alpine biking, braking can occur dozens of times a minute. Energy is lost each time the brake is applied. If the kinetic energy can be stored, even in part, while the bicycle decelerates and the energy used to accelerate the bicycle after braking, a significant increase in overall efficiency is realized.
By employing a triple ratchet torsional spring apparatus mounted in the hub of the bicycle, the spring can be charged and discharged by the braking action of the rider. One end of the spring is connected to a braking apparatus and the other end is connected to the hub thus allowing the spring to apply a torsional moment, opposing the direction of travel of the bicycle, thereby supplying the braking force. A ratchet is interposed at each connection to restrict the motion of the spring and hub to one direction only. When the braking force is released, the charged spring then drives the bicycle in the forward direction until it is fully discharged. This is not intended as an alternative to pedalling but rather to be used in conjunction with pedalling to augment the power source.
The braking apparatus is useful in relatively small vehicles such as bicycles, golf carts, solar vehicles, mopeds and go-carts. Briefly, the regenerative braking and driving apparatus of the invention comprises resilient means operatively connected to a wheel; deforming means which when activated causes the resilient means to resiliently deform with resulting braking of the wheel and which, when de-activated, allows the resilient means to return to an undeformed state. The resilient means, as it returns drives the wheel forward.